1. Field of the Invention
The invention disclosed herein relates to an apparatus, system and method for treating domestic wastewater and sewage.
2. Description of Prior Art
Residential dwellings are constructed with various systems to be fit for human habitation, including some means for disposing of sewage and wastewater produced by the dwelling's inhabitants. Dwellings located in urban or municipal areas are usually connected to a network of sewer pipelines, which route wastes to a central treatment works. Dwellings in rural areas, on the other hand, usually have some form of partial or full treatment system located on site. These on-site treatment systems include anaerobic treatment systems, such as cesspools or septic tanks, and aerobic systems, such as aerated treatment tanks.
Anaerobic treatment systems treat domestic waste and waste water using anaerobic, or “without oxygen” bacteria. The septic tanks used in such systems are simple, comprised of a subsurface concrete or steel tank, an inlet pipe for charging waste into the tank, and an outlet pipe. In the tank the waste resides for a length of time, during which it separates into sludge, liquid and scum layers. The sludge layer, which settles and accumulates on the bottom of the tank, contains most of the pollutants and solids in the domestic waste and is gradually degraded by anaerobic bacteria. After the solids settle from the liquid, the liquid layer is discharged from the septic tank through the outlet, usually through some form of baffle to prevent the discharge of any floating scum or settled sludge, as well.
The separation and anaerobic degradation of the solids is, however, slow and inefficient. As a result, the liquid effluent from the outlet of a septic tank still contains dissolved and suspended pollutants, odors and possible pathogens, and is not suitable to discharge to a surface waterway. Typically, the effluent from a septic tank is discharged to a drainage field or leach field, consisting of one or more parallel trenches with subsurface perforated pipes. The effluent is discharged through the perforations, from where it leaches into the subsoil and is further decomposed and degraded by soil bacteria prior to merging with the local groundwater table.
Aerobic systems, on the other hand, utilize aerobic, or “with oxygen” bacteria, which are more effective than anaerobic bacteria. An aerobic treatment system usually consists of two tanks or chambers; the first in which waste is mixed into a slurry with entrained and dissolved air, which promotes the growth and activity of aerobic bacteria. Air is introduced into the waste slurry in the mixing chamber either by an air sparger, which is a pipe with one or more openings placed below the slurry level, through which pressurized air is injected into the slurry, or by a diffuser, similar to an agitator or propeller, which rotates in the waste slurry and draws air from the vapor space above the slurry down into its blades and mixes with the slurry.
After a sufficient average residence time in the mixing chamber, the waste slurry flows into the second, settling chamber, where the solids settle into a sludge layer on the bottom of the chamber. The clarified liquid is discharged from the settling chamber, usually through a baffle to prevent discharge of any floating waste material. Because of the greater efficiency of aerobic bacteria, the effluent from an aerobic system is usually treated sufficiently for discharge to a surface water body, such as a stream, except for some quantity of residual bacteria, which are easily treated with a final chlorination step. For this, a chlorinating device is positioned in the effluent of the aerobic system, either within the settling chamber or as a separate chamber adjacent to the settling chamber.
As described above, a septic system includes a drainage field, where the remainder of the necessary treatment on the waste water occurs. However, this subsoil treatment encourages and promotes the growth of bacteria in the subsoil, which over time results in a slime filling and blocking the pores and interstitial spaces of the subsoil. When this occurs, the subsoil is no longer permeable and the septic system can no longer function properly. In this event, either a new drainage field must be installed down grade of the septic tank, or, if no suitable soil is available for a new drainage field, the entire system must be replaced with an aerobic system.
The latter scenario has become common in rural areas such as in the Appalachian region. Many properties in rural Appalachia have shallow, clay soils with limited permeability. These properties are often located adjacent or near to small surface water bodies. As the drainage fields in existing septic systems fail, the lack of suitable soil and more stringent water pollution control regulations proscribe the installation of another drainage field.
In many of these situations, the only alternative available is the installation of an aerobic treatment system, due to the ability of an aerobic system to discharge to surface waters and the availability of potential receiving water bodies in the Appalachian region. However, at present, a switch to an aerobic treatment system requires the installation of a complete, new system and abandonment of the septic tank as well as the drainage field of the failed anaerobic system. In abandoning the septic tank, a valuable piece of equipment is lost which is capable of functioning as part of an aerobic system through a retrofit or conversion, that could thereby reduce the cost of the new system installation.